The present invention relates to drafting boards and more particularly to a drafting board having a straight-edge assembly with a ruling edge that is movable with respect to a drawing surface such that the ruling edge is positionable at various selected angles relative to the front edge of the drawing surface.
Drafting boards having a movable straight-edge assembly have been known heretofore. Movement is generally effected by means of cooperable gear and track elements. The gear and track elements. The gear elements are usually mounted at the ends of a rigid shaft and are movable as a unit to thereby shift a ruling edge between the front and rear edges of a drawing surface while maintaining the ruling edge in parallel relation to such front edge. A typical prior art drawing board structure of this character is disclosed in U.S. Pat. No. 2,577,159 issued Dec. 4, 1951 to P. Seferow. A prior structure in which some adjustment of the straight-edge assembly is permitted is disclosed in U.S. Pat. No. 2,701,918 issued Feb. 15, 1955 to G. Phelps. However the lateral ends of the straight-edge assemblies of Seferow and Phelps move across the drawing surface essentially as a unit and so as to maintain the ruling edge in parallel relation to the front edge of the drawing surface. There has thus been no capability in prior drafting board structures for the ready and accurate positioning of the ruling edge in a variety of selected angles relative to the front edge of the drawing surface to permit the drawing of lines throughout a wide range of angular settings.